Polyalkylene carbonates are non-crystalline transparent resins. Unlike aromatic polycarbonates that are engineering plastics of a similar type, polyalkylene carbonate has advantages of being biodegradable, of being thermally decomposed at a low temperature, and of being completely decomposed into carbon dioxide and water without a remaining carbon residue.
The preparation of polyalkylene carbonate is conducted in the presence of a chlorinated solvent, and after polymerization, many different impurities are present in the polymerization products.
The production process of polyalkylene carbonate is largely divided into a polymerization process and a post-treatment process. The post-treatment process includes a process of removing residual monomers and impurities other than polyalkylene carbonate and carrying out pelletization of the polyalkylene carbonate.
Kinds of the residual monomers recovered and the impurities removed in the post-treatment process are as follows.
The residual monomers include carbon dioxide and ethylene oxide, and the impurities include catalyst residues, by-products, and solvents.
The catalyst residues include Zn-based catalysts and the by-products include ethylene carbonate.
Among them, the catalyst residues induce polymer degradation when they are not removed. Therefore, it is very important to remove the catalyst residues.
However, the existing methods have a problem of polymer degradation which is caused by the presence of a part of the catalyst residues.